The London tube network is one of the oldest in the world, so it comes as no surprise that buried within it are plenty of secrets.
Who better to ask about them than a London tube driver?
One volunteered themself on Reddit to answer people's burning questions - and the answers are as fascinating as you would predict.
Not every train driver is a train geek.
Drivers have secret special toilets - and hidden places to make a cup of tea - because this is Britain.
The skill requirement differs greatly between lines.
Passengers can do some strange things.
Drivers can wear company-issued shorts - and it's probably not as hot for them as the it is for you.
TFL is progressive when it comes to gender, not allowing drivers to say "ladies and gentleman".
The pay is good, though it can be hard to land the job.
This is what the dreaded 'signal failure' actually means.
Even tube drivers appreciate fun announcements.
More: The 12 weirdest images commuters have taken